A use case describes, from a
user's
perspective, a behaviourally related set of
transactions that are normally performed together to produce some
value for the user. Use cases can be represented graphically in a a use case
diagram as an oval shape, each use case being described in the
data dictionary. Use cases may be modelled at varying degrees of
abstraction:
essential use cases, the most abstract, are technologically and implementation
independent whereas
real use cases describe how the use case actually operates in a particular environment.
Source: Bennet, S (1999) Object-Oriented Systems Analysis and Design using UML. McGraw Hill, Great Britain.